The present invention relates to an apparatus for comminuting and mixing of foodstuffs, and more particularly to such an apparatus which is of the upright type.
Generally speaking, apparatuses for mixing and comminuting of foodstuffs come in two basic types, a horizontal type where the drive for the mixing arrangement in the bowl of the apparatus is located laterally of the bowl, and the upright kind wherein the drive is located beneath the bowl. The latter type, with which the present invention is concerned, is known for example from U.S. Pat. No. 2,918,956 and from U.S. Pat. No. 3,612,546. This type of apparatus requires that the drive shaft of the motor which is located beneath the mixing bowl, extend through an opening in the bottom wall of the bowl into the interior of the latter, where it is suitably connected with the mixing instrumentalities to be rotated, such as blades or the like.
The difficulty with upright comminuting and mixing apparatuses known from the prior art is that significant problems have been encountered in sealing the opening in the bottom wall through which the drive shaft extends into the interior of the bowl. Various types of seals have been utilized, including an arrangement which includes two successively arranged seals which are mounted in a plate that is constructed as a sealing flange and is threadedly connected to the bottom wall of the bowl. This latter type of seal is by far the most satisfactory of the ones that have become known from the prior art. However, it is quite complicated in its structure, and therefore not only difficult to install, but also difficult to maintain and repair. Moreover, this type of seal is subject to a substantial amount of wear.
A further drawback of the prior-art upright machines of the type in question is that because of their construction they must be relatively tall. This causes problems in certain applications, because the machine is too tall to be placed onto a table and conveniently operated, the upper open end of the machine through which material is admitted being then located too high for convenient access by an operator. On the other hand, the machines cannot be placed on the floor because they are too low for convenient operation when this is done. This requires special supporting arrangements which support the machine at an intermediate height where it can be conveniently operated. This, however, also involves additional expense and inconvenience.
Still another drawback of the prior-art machines of the type in question is that they have relatively complicated and elaborate (and hence, costly) safety arrangements whose purpose it is to switch off the drive for the comminuting instrumentalities in the interior of the bowl when the cover that is provided on the bowls of such machines, is removed. While such safety arrangements are of course highly desirable, it is equally desirable to simplify them in order to reduce the expense of constructing the machine and, not the least, in order to reduce --by reducing the complexity of the arrangement-- the possibility of malfunction.